Thyroid malignancies: a New Zealand South Island thyroid clinic experience 1995-2006

To assess the number and histological type of thyroid malignancies occurring in the northern half of New Zealand's South Island (referral population of 553,000).

Patients with newly diagnosed thyroid malignancies seen at thyroid clinic, Christchurch Hospital between 1995 and 2006 were identified from the thyroid clinic database, and the histological diagnoses and clinical features were reviewed from hospital records.

During the 12-year study period, 213 patients with thyroid malignancy were identified. The majority had thyroid cancer of follicular cell origin--184 differentiated thyroid cancers (DTC) and 9 anaplastic thyroid cancers. The DTC patients included 130 with papillary thyroid cancers (PTC)--71%; 33 follicular thyroid cancers (FTC)-18%; and 21 Hurthle cell thyroid cancers (HTC)-11%. One of the papillary cancer patients had a mixed papillary-medullary tumour. The 184 DTC patients included five patients with an immediate family member with thyroid cancer--including a mother-son pair with papillary cancer. Tumours of nonfollicular cell origin included 12 medullary thyroid cancers (6% of primary thyroid malignancies), and all were apparently sporadic, 7 primary thyroid lymphomas, and 2 thyroid metastases. The female-male ratio was >/=2 in all patient groups with primary thyroid malignancies. The median age for both PTC and FTC groups was 48 y, with Hurthle cell, anaplastic, and lymphomas occurring in older patients. The 3 paediatric patients (<16 y) all had PTC.

In the 12-year study period the majority (90%) of thyroid malignancies were of follicular cell origin--184 DTC (papillary 130, follicular 33, and Hurthle 21), and 9 anaplastic cancers. Tumours of non-follicular cell origin were uncommon and included medullary cancers, lymphomas, and metastases. Short-term follow up (median 6 y) confirms that anaplastic thyroid cancer is highly malignant, and the only patients with differentiated thyroid cancer with early cancer deaths had presented with advanced disease and were > 55 years at diagnosis.